Questions tagged [radio-frequency]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
1 vote
0 answers
25 views

Radiowave diffraction

When a far field propagated radio wave encounters an obstacle such as a mountain does the radio wave actually bend around the mountain? In other words should my receiving antenna on the other side of ...
user avatar
  • 11
0 votes
4 answers
69 views

Superposition of EM waves and "magic" behind tuned receiver circuit

I'm struggling to understand how the receiver circuit (eg. FM radio) is able to extract a particular frequency out of the sum of all received frequencies by its antenna? I've checked dozen of websites,...
user avatar
0 votes
0 answers
17 views

Hypothetical NMR experiment

Say I set the RF of NMR to resonate to a specific frequency of a specific isotope of nitrogen, based on the magnetic field strength of the NMR machine, Now, imagine if I had put in egg whites(or any ...
user avatar
0 votes
0 answers
7 views

Wireless Power Transfer in Layered Material

I’m looking to develop a mathematical model for near-field electromagnetic power transfer through layers of human tissue, from an external transmitting antenna to an embedded antenna. Each tissue ...
user avatar
0 votes
1 answer
17 views

Frequency upconversion of pulses shorter than 1 IF period

I have a rather elementary frequency upconversion/mixer question, perhaps so simple that it does not warrant a real question but rather just a reference to a website/tutorial (that I have not been ...
user avatar
  • 1,349
0 votes
3 answers
91 views

How are sidebands generated in an AM signal?

I can't understand how sidebands get generated, even after reading this wikipedia page: https://en.wikipedia.org/wiki/Sideband#Amplitude_modulation This is how I picture Amplitude Modulation in its ...
user avatar
  • 105
0 votes
1 answer
35 views

Scattering off upside-down parabolic reflector (radio frequency)

Suppose I have a steel frame parabolic reflector with a handful of steel wire supports. The size is approximately 10m high and 20m in radius. Assume the gaps in the triangular trusses are roughly 3m. ...
user avatar
8 votes
1 answer
222 views

Why is a magnesium flame changing color in an electromagnetic field?

On YouTube I have seen someone build a RF emitter (probably in the 10 MHz range with about 5000 Watts) and then use it to ignite magnesium strips. Magnesium usually burns with a bright white flame in ...
user avatar
  • 602
0 votes
1 answer
59 views

Do electrons in EM waves literally travel in space, or they just move like a rope being swung at an end

Electrons do actually move in a closed circuit as explained in this video: https://youtu.be/8gvJzrjwjds?t=85 They jump from atom to atom. But what about electromagnetic waves, or more specifically ...
user avatar
  • 105
0 votes
0 answers
149 views

How would an AM and FM wave change when the input signal increase in loudness or frequency?

I am currently studying for the A levels and am a bit confused about how an AM and FM wave will change when the wave isn't sinusoidal and have differing frequency and loudness. I understand how a ...
user avatar
  • 1
1 vote
0 answers
66 views

Why are smartphone antennas not $\lambda/2$ of the wavelength? Why are patch-antennas used instead of simple dipole antennas? [closed]

Why are smartphone antennas not $\lambda/2$ of the wavelength? Why are patch-antennas used instead of simple dipole antennas? I'm very new to this but really interested in using basic physics to ...
user avatar
  • 395
2 votes
1 answer
57 views

Can radio waves be converted to positron and electron when placed in weak electric field?

In particle physics, gamma rays can be converted to positron and electron when placed in strong electric field. My question is: What will happen if radio waves are placed in weak electric field? Will ...
user avatar
  • 23
0 votes
0 answers
16 views

Can we express Free-space path loss formula in the following pointwise way?

We know that the Free-space path loss formula is of the form $$\frac{P_{r}}{P_{t}}=D_{r}D_{t}\left(\frac{\lambda}{4\pi d}\right)^{2} $$ $D_{r}, D_{t}$ are the directional gains of the receiver and the ...
user avatar
1 vote
3 answers
60 views

What are the advantages of radio spectroscopy? [closed]

What is the main purpose for radio spectroscopy? What information of the atomic structure of atoms can we gain from using radio frequency radiation rather than X-rays? Since the wavelength of radio ...
user avatar
0 votes
1 answer
23 views

Over what distance might this device be able to interfere with car radios?

I've been reading recently about a mysterious and possibly hokey medical device of the 1930s. It was a variable-frequency radio emitter, invented by a Dr. Rife, which was supposed to kill various ...
user avatar
  • 61
1 vote
3 answers
206 views

Theoretically, could radio waves carry enough energy to destroy bacteria or viruses by resonance?

I've been reading recently about a mysterious and possibly hokey medical device of the 1930s. It was a variable-frequency radio emitter, invented by a Dr. Rife, which was supposed to kill various ...
user avatar
  • 61
1 vote
1 answer
29 views

What happens to Langmuir waves at a density gradient in plasmas?

I'm trying to understand a little bit of what happens to electrostatic Langmuir waves when there is an initial density gradient present. The plasma frequency depends on the density, so you would ...
user avatar
  • 11
2 votes
1 answer
422 views

Is it okay to sleep with the wifi router next to me?

Where I sleep I have my wifi router right above me. I don't know if this is safe for my health since it emits radiation. Some people say that it should be safe since the radiation emitted is non-...
user avatar
0 votes
1 answer
46 views

Why does amplitude modulated wave take the frequency of a carrier signal when passed through air?

If a message signal of frequency $f_m$ is amplitude modulated with a carrier signal of frequency $f_c$ and radiated through an antenna, the wavelength of the corresponding signal in air is ans: $\frac{...
user avatar
0 votes
1 answer
55 views

Radiowaves and electromagnetic waves

I have a simple question: What part of physics study radiowaves and electromagnetic waves? Can you link a source where can I find basics of radiowaves pdf or something?
2 votes
2 answers
78 views

Single photon radio wave [duplicate]

If there is a single photon representing a radio wave with wavelength say 10 m, what does this 10 m really mean? Does it mean that the photon itself could be anywhere in those 10 m?
user avatar
0 votes
2 answers
42 views

Multipoint impedance matching to RF plasma

When dealing with RF plasma sources - one of the most significant challenges is impedance matching between RF power source and plasma. Impedance of plasma changes dramatically during ignition - and ...
user avatar
  • 2,832
2 votes
1 answer
43 views

What is the explanation behind radio shadowing by people?

I called it shadowing but masking may be more appropriate, feel free to suggest a better question title after you read the following. I have an old clock alarm radio receiver that plays at the center ...
user avatar
  • 3,179
0 votes
1 answer
90 views

What is the most accurate instrument which can be used to measure frequency of radio waves without measuring wavelength and how accurate is it?

I wanted to know if there's an instrument that accurately measures the frequency of radio waves as I'm working on something and I didn't get anything good on web.
user avatar
0 votes
2 answers
59 views

X-rays are absorbed by bone. If the width of the bone increased in proportion to the wavelength, would bone absorb radio waves?

What I’m interested in here, are the properties of different electromagnetic waves, and the factors that cause them to be absorbed by different materials and be influenced in other ways by different ...
user avatar
  • 103
1 vote
1 answer
30 views

What causes the sudden change in atmospheric reflection of long-band radio waves?

This picture shows up a lot. The explanations that tend to accompany it say that the long-band radio waves above ~10m are reflected, whereas other wavelengths are scattered or absorbed or transmitted. ...
user avatar
  • 1,335
1 vote
0 answers
21 views

is room temperature quantum (qubit) nuclear magnetic resonance possible?

I know it is possible to do room temperature NMR. Not just that but one can also use the earth's magnetic field for the nuclei to precess about. If done this way, one gets precession at about the KHz ...
user avatar
12 votes
3 answers
2k views

How does the human body affect radio reception?

My sister asked me why her small radio sometimes has better reception when she places her hand nearby (without touching) the antenna. I did some research and wanted to ask a few questions. Here are ...
user avatar
0 votes
0 answers
57 views

Lens Design 60GHz Radar

I'm trying to design a lens for a 60GHz radar chip however rather than focusing the radar beam I'd like to widen it to a specific width. Also, the radar antenna has a main beam width that is larger ...
user avatar
  • 101
2 votes
3 answers
103 views

How are phased arrays compatible with the photon concept?

Not a physicist (although I know how to develop and simulate phase arrays). Phased arrays are e.g. emitters sending waves with individual elements with a different phase so that they act ...
user avatar
  • 3,179
0 votes
1 answer
47 views

Extreme Redshift Detection

There is a new paper in arXiv postulating that black holes might actually let some let some light out. This of course is very theoretical, but it postulates that the light would be redshifted to 640 ...
user avatar
0 votes
1 answer
56 views

How do the arc and the straight line have equal length in this figure?

I have the following derivation in one of my physics problem related to range of a transmitting antenna: How is the distance QT equal to the length of arc PT? Can someone provide a quick explanation ...
user avatar
1 vote
2 answers
56 views

Why do artificial transmissions of coherent EM waves tend to be isotropic at radio frequencies but directional at visible frequencies?

This is a somewhat soft question, and I'm far from an expert on the subject, so it's possible that my premise is factually incorrect. The practical generation mechanisms for useful real-world coherent ...
user avatar
  • 41.3k
0 votes
1 answer
33 views

Doubt in radar question

This is a question(2.25) from introduction to radar systems by Merrill Skolnik 3rd edition. Plot the single-scan probability of detection as function of range, assuming a constant cross-section target ...
user avatar
  • 11
0 votes
0 answers
50 views

Building a radio telescope!

So, I saw recently the idea of a radio telescope and thought how simple they are. So, like any other normal human being, I went on google and searched "how to make a radio telescope" and ...
user avatar
0 votes
1 answer
23 views

Is there a frequency converting amplifier? [closed]

Frequency conversion means output of the amplifier is at a frequency different from that of the input.
user avatar
0 votes
1 answer
42 views

What are odd radio circles (ORCs) in Space?

There is a video (https://www.youtube.com/watch?v=jXnXbMcI8Lo&t=595s) about pure radio waves radiating in circles in space. Odd radio circles (ORCs) are not radiating any other wave length (...
user avatar
  • 2,371
1 vote
0 answers
89 views

Complex reflection coefficient for a radio frequency wave

With an RF transmitter at location $P_1$ and a receiver at $P_2$, I would like to calculate how much power reaches $P_2$ via a reflection at a point $P_3$. Hence I need to know the reflection ...
user avatar
  • 141
2 votes
1 answer
155 views

Proxima Centauri radio signal

I have recently seen an article about an unusual radio signal coming from Proxima Centauri region. I understand there is a debate around the nature of this signal. My question is related to this ...
user avatar
  • 611
0 votes
1 answer
22 views

How does UWB enable much higher positioning accuracies than Narrowband

literature and internet articles often only explain UWB’s much higher positioning accuracies with its much higher bandwidth compared to the bandwidth of other narrowband technologies such as WiFi/...
user avatar
  • 1
1 vote
0 answers
25 views

Is it possible to filter radio-waves using another radio telescope?

When making an observation using a radio telescope, is it possible to filter out noise coming out from a known source by using another telescope that will focus on that noise source? By filtering, I ...
user avatar
  • 1,855
0 votes
0 answers
51 views

How does oxygen react to radio waves at 60Ghz?

Since there are 3 states of oxygen: 3Σ−g: The ground triplet state 1Δg: The ground singlet state 1Σ+g: An excited singlet state. What happens to the ground triplet state when it is exposed to the 60 ...
user avatar
0 votes
1 answer
32 views

Frequency modulation with a certain bandwidth

I came across this sentence in this paper. Alternatively, we modulate the frequency of the microwave excitation voltage at 971 Hz with a square wave and a bandwidth of 32MHz. In my limited FM ...
user avatar
0 votes
1 answer
405 views

Modulation Index of an AM wave

I have been given a question as RMS value of an RF(Radio Frequency) voltage after amplitude modulation to a depth of $50$% by a sinusoidal voltage is $80$ Volts. Calculate the RMS value of modulated ...
user avatar
0 votes
0 answers
25 views

How does Tx Power affect the Free Space Path Loss model?

On this website one can use the FSPL model to calculate the Path Loss. This is typically interpreted online as the theoretical signal strength (in dB) that one may receive (e.g. from some WiFi). ...
user avatar
  • 101
1 vote
1 answer
48 views

How much does the sun emits in the radio spectrum, compared to artificial (human) emissions?

I would like to compare natural vs artificial (human) emissions in the radio spectrum (f < 1 THz). The goal is to bring some scientific facts in the debate for deployment of 5G. It's easy to find ...
user avatar
0 votes
1 answer
60 views

In what media the speed of light is slower than the speed of radio waves, if any?

In what media the speed of visible light is slower than the speed of radio waves, if any? Particles can be faster than visible light, but other electromagnetic waves?
user avatar
0 votes
0 answers
44 views

S-matrix for 2-port network

Consider an impedance $Z$ on a waveguide of impedance $Z_0$. I add a load $Z_L$ at the end of the line but I don't think it should enter in the calculation ? I call $1$ the left port, $2$ the right ...
user avatar
  • 1,034
-1 votes
1 answer
51 views

Will a sheet of carbon atoms reflect radio waves?

I am working out some details in a SciFi novel. I'm thinking of having spec ops who would use a device that could manipulate carbon atoms to form and maintain large, rigid, one-atom thick carbon ...
user avatar
  • 107
1 vote
1 answer
71 views

How I simulate this in CST Studio? [closed]

I am trying to simulate this coaxial transmission line setup for EMI shielding. Placed the Aluminium sample as seen below (in the middle). I am new on this software, learned simulating the coaxial ...
user avatar
  • 11

1
2 3 4 5 6